Table 1.
Participants’ characteristics at baseline by pain phenotypes *.
| Characteristics | Class 1 (n = 236) |
Class 2 (n = 193) |
Class 3 (n = 534) |
p† C1 vs. C2 |
p† C1 vs. C3 |
p† C2 vs. C3 |
|---|---|---|---|---|---|---|
| Age (years) | 63.1 ± 7.7 | 64.4 ± 7.4 | 62.1 ± 7.2 | 0.217 | 0.242 | 0.001 |
| Female sex, n (%) | 152 (64) | 66 (34) | 267 (50) | <0.001 | <0.001 | <0.001 |
| BMI (kg/m2) | 29.0 ± 5.4 | 29.4 ± 4.5 | 26.5 ± 3.9 | 0.869 | <0.001 | <0.001 |
| Presence of emotional problems, n (%) | 218 (92) | 97 (50) | 298 (56) | <0.001 | <0.001 | 0.040 |
| Emotional problems, n (%) | <0.001 | <0.001 | 0.003 | |||
| Not at all | 18 (8) | 96 (50) | 236 (44) | |||
| Very little | 94 (40) | 69 (36) | 185 (35) | |||
| Moderately | 86 (36) | 22 (11) | 84 (16) | |||
| Quite a lot | 35 (14) | 5 (3) | 27 (5) | |||
| Extremely | 4 (2) | 1 (1) | 2 (0.4) | |||
| Education level, n (%) | <0.001 | <0.001 | <0.001 | |||
| School only | 160 (68) | 77 (40) | 296 (55) | |||
| Vocation training | 74 (31) | 77 (40) | 164 (31) | |||
| University or higher | 2 (1) | 39 (20) | 74 (14) | |||
| Presence of any comorbidity, n (%) | 162 (69) | 98 (51) | 198 (37) | <0.001 | <0.001 | <0.001 |
| WOMAC pain score (0–45) | 8.6 ± 8.6 | 3.2 ± 5.6 | 1.5 ± 3.0 | <0.001 | <0.001 | 0.001 |
| Number of painful sites (0–7) | 5.8 ± 1.1 | 2.4 ± 1.5 | 2.2 ± 1.7 | <0.001 | <0.001 | 0.265 |
| Presence of radiographic knee OA, n (%) | 156 (66) | 131 (67) | 290 (54) | 0.791 | 0.004 | 0.004 |
| Knee structural pathology, n (%) | ||||||
| Cartilage defects | 88 (37) | 172 (89) | 60 (11) | <0.001 | <0.001 | <0.001 |
| BMLs | 82 (35) | 161 (83) | 101 (19) | <0.001 | <0.001 | <0.001 |
| Effusion-synovitis | 102 (43) | 125 (65) | 184 (34) | <0.001 | 0.026 | <0.001 |
* Values are the Mean ± SD except for percentages and pain phenotypes (Classes) were identified from latent class analysis. † p values are from post hoc testing for comparisons between classes determined by ANOVA or logistic regression (where appropriate); BMI body mass index; WOMAC Western Ontario and McMaster Universities Osteoarthritis Index; OA osteoarthritis; BMLs bone marrow lesions. This table has been published elsewhere [16] and permission to use has been obtained.